This invention relates to the art of blow molding articles of organic plastic material from a parison and has for its principal object the improved, substantially uniform adjustment of the temperature of the parison, the provision of improved, oriented hollow articles and a method and apparatus for obtaining same.
The art teaches various methods and apparatus for obtaining blow molded articles of organic plastic material from a parison, such as in U.S. Pat. No. 3,349,155 and U.S. Pat. No. Re. 27,104. Generally these methods are characterized by forming a parison in a parison mold on a blow core, placing said formed parison and blow core into a blow mold and expanding said parison in the blow mold by means of fluid pressure.
While the blow molding operation tends to impart orientation to the article, the degree of such orientation is difficult to control and therefore it is difficult to obtain the advantageous properties in the article that orientation is capable of providing if said orientation is carried out under the most desirable conditions.
It is known that the control of orientation depends largely upon the control of the temperature of the parison just prior to orientation. It is found that such temperature control is best obtained by enclosing the article prior to the orienting step in a mold whose surfaces provide conductive contact with the corresponding surfaces of the article.